The present invention relates to a voltage control apparatus of an engine generator which controls an output voltage of an automatic voltage regulator (AVR) of an engine generator, and a control method thereof.
An engine generator is widely used as a movable power source in a field of construction work or the like, an emergency power source in a building, a plant, a hospital or the like, or a permanent power source in an area where a commercial power source can not be obtained. In the engine generator, when a load suddenly increases due to a load input, an output of an engine driving the power generator can not follow an increase of the load, so that an engine rotational speed is largely reduced in a moment. Since this reduction of the engine rotational speed gives a bad influence to the load maintained in the power generator, it is defined so as to set a reduction rate with respect to a rated rotational speed and a time required after the rotational speed is reduced and before being returned to the rated rotational speed to be within a predetermined range.
When the load of the engine generator is suddenly increased, the engine rotational speed is reduced and a governor is operated in accordance therewith so as to increase a fuel injection amount. However, since the power generator is generally driven by an engine with a supercharger, an increase of a pressure of a supplied air is delayed in comparison with an increase of a fuel injection amount. Accordingly, a recovery of the engine rotational speed is delayed. Then, a lot of techniques for quickening a recovery of the engine rotational speed have been conventionally suggested. For example, in accordance with a technique disclosed in Unexamined Japanese Patent Publication No. 5-111298, an output voltage control for reducing an energizing current of an automatic voltage regulator only for a fixed time at a fixed rate so as to descend an output voltage thereof is performed as means for temporarily reducing a load applied to the power generator.
However, since the control in accordance with the technique mentioned above is performed by a load information in the power generator side such as the output current or the output power of the power generator and the like, an output current sensor, an output power detector and the like are required. Since the load of the power generator generally corresponds to a great energy, and the output voltage value and the output current value correspond to great values, the output current sensor, the output power detector and the like for detecting them are set to be a large scale having a great energy resisting amount. Accordingly, the control apparatus tends to be formed in a large scale, a structure thereof is complex and a cost therefor is increased. Further, a large space for placing the sensors and the control apparatus is required and it is hard to make the engine generator compact.
The present invention is made by taking the problems mentioned above in the prior art into consideration, and an object of the present invention is to provide a voltage control apparatus of an engine generator having a simple structure and capable of being made compact, and a control method thereof.
In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a method of controlling a voltage of an engine generator comprising the steps of:
detecting an actually measured value of an engine rotational speed at every predetermined time; and
controlling an output voltage of the power generator in accordance with a deviation value between a predetermined target value and the actually measured value when the actually measured value is equal to or less than the target value.
In accordance with the first aspect, since a degree of the load applied to the power generator is judged on the basis of the engine rotational speed and the output voltage of the power generator is controlled in accordance with the deviation value between the predetermined target value and the actually measured value of the rotational speed, that is, in accordance with a degree of change of the rotational speed, it is possible to reduce the output voltage in accordance with a magnitude of the sudden load change. Accordingly, since the control is not performed by detecting the output current, the output power or the like in the power generator side which is employed in the conventional art, it is possible to restrict a change width and a change time of the output voltage, the frequency and the like of the power generator to a minimum limit at a sudden load transient time so as to move to a stable operation by utilizing the rotational speed detector particularly in the case that an electronic governor is provided. In general, since the rotational speed detector has a small energy resisting amount and is compact, it is possible to manufacture the control apparatus in accordance with the voltage control method at a low cost and in such a manner as to be compact.
In accordance with a second aspect of the present invention, there is provided a method of controlling a voltage of an engine generator comprising the steps of:
detecting an actually measured value of a fuel injection amount of an engine and an actually measured value of a rotational speed at every predetermined time; and
controlling an output voltage of the power generator in accordance with a deviation value between a predetermined target value of the fuel injection amount with respect to the actually measured value of the rotational speed and the actually measured value of the fuel injection amount.
In accordance with the second aspect, since a degree of the load applied to the power generator is judged on the basis of the fuel injection amount of the engine and the output voltage of the power generator is controlled in accordance with the deviation value between the target value of the fuel injection amount with respect to the actually measured value of the rotational speed of the engine and the actually measured value of the fuel injection amount, that is, in accordance with a degree of change of the fuel injection amount, it is possible to reduce the output voltage in accordance with a magnitude of the sudden load change. At this time, since it is possible to control the output voltage of the power generator even when the actually rotational speed is higher than the target value of the rotational speed in the first aspect, that is, an engine rotational speed for starting control, it is possible to detect a load increase in the power generator at an early time so as to reduce the load. Accordingly, since the control is not performed by detecting the output current, the output power or the like in the power generator side which is employed in the conventional art, it is possible to restrict a change width and a change time of the output voltage, the frequency and the like of the power generator to a minimum limit at a sudden load transient time so as to move to a stable operation by utilizing the rotational speed detector and the fuel injection amount detecting means particularly in the case that an electronic governor is provided. In general, since the rotational speed detector and the fuel injection amount detecting means has a small energy resisting amount and is compact, it is possible to manufacture the control apparatus in accordance with the voltage control method at a low cost and in such a manner as to be compact.
In accordance with a third aspect of the present invention, there is provided a method of controlling a voltage of an engine generator comprising the steps of:
detecting an actually measured value of a rotational speed of an engine and an actually measured value of a fuel injection amount at every predetermined time;
controlling an output voltage of the power generator in accordance with a deviation value between a predetermined target value of the fuel injection amount with respect to the actually measured value of the rotational speed and the actually measured value of the fuel injection amount when the actually measured value of the rotational speed is greater than the predetermined target value; and
controlling the output voltage of the power generator in accordance with a deviation value between a predetermined target value and the actually measured value of the rotational speed when the actually measured value of the rotational speed is equal to or less than the predetermined target value.
In accordance with the third aspect, since the degree of the load of the power generator is judged on the basis of the rotational speed of the engine and the fuel injection amount and the output voltage of the power generator is controlled in accordance with the deviation value of the rotational speed and the deviation value of the fuel injection amount, that is, in accordance with the degree of change of both of the rotational speed and the fuel injection amount, it is possible to perform a control having an improved response and a high accuracy.
In particular, since an output voltage of a power generator is controlled in accordance with a target value Q1 and an actually measured value Q of a fuel injection amount when an actually measured value Ne of the rotational speed is not reduced to a predetermined target value Ne1, it is possible to early know an increase of load so as to immediately reduce the load, thereby controlling with an improved response at a transient time when the load of the power generator is suddenly changed. Further, since the output voltage of the power generator is controlled in accordance with the target value Ne1 and the actually measured value Ne of the rotational speed when the actually measured value Ne of the rotational speed is reduced to a level equal to or less than the target value Ne1, the rotational speed is securely controlled to be restored to a value equal to or more than the target value Ne1, whereby it is possible to accurately control at a sudden load transient time. Accordingly, since the control is not performed by detecting the output current, the output power or the like in the power generator side which has been performed in the prior art, in particular in the case that the electronic governor is attached, it is possible to restrict a change range and a change time of the output voltage, the frequency and the like in the power generator at a sudden load transient time to a minimum limit by utilizing the rotational speed detector and the fuel injection amount detecting means so as to move a stable operation. In general, since the rotational speed detector has a small energy resisting amount and is compact, it is possible to manufacture the control apparatus in accordance with the voltage control method at an inexpensive cost and in a compact size.
In accordance with a fourth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the second aspect or the third aspect, wherein when controlling the output voltage of the power generator in accordance with the deviation value between the predetermined target value of the fuel injection amount with respect to the actually measured value of the rotational speed and the actually measured value of the fuel injection amount, in the case that the actually measured value of the fuel injection amount is equal to the predetermined target value, the output voltage of the power generator is controlled in accordance with the deviation value between the predetermined target value of the rotational speed and the actually measured value thereof.
In accordance with the fourth aspect, since the structure is made such as to finish the control on the basis of the deviation value of the fuel injection amount and immediately control in accordance with the deviation value of the rotational speed in the case that a target value Q1 of the fuel injection amount and an actually measured value Q thereof are equal to each other when controlling the output voltage of the power generator in accordance with the deviation value between the target value Q1 and the actually measured value Q, it is possible to securely control the rotational speed to a level equal to or more than a predetermined target value. Accordingly, it is possible to accurately move the sudden load transient characteristic of the power generator to a stable operation.
In accordance with a fifth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the first aspect, the second aspect or the third aspect, wherein when the actually measured value of the engine rotational speed is equal to or more than a second target value lower than the first target value, a state having a rotational speed lower than the first target value continues and the continuing time is over a predetermined first threshold during the output voltage control of the power generator, a control of returning the power generator to a rated output voltage is performed.
In accordance with the fifth aspect, when the actually measured value of the engine rotational speed is lower than the first target value and the state of being equal to or more than the second target value continues for the predetermined time or more, the voltage adjustment function by the automatic voltage adjuster is operated so as to be controlled to the rated voltage by performing the control of returning the voltage from the output voltage which is lower than the rated voltage to the rated voltage. Accordingly, since the time for which the power generator outputs the voltage which is lower than the rated voltage becomes within the predetermined time, it is possible to control the output voltage reduction time of the power generator in a standard manner, and it is also possible to restrict the change of the output voltage.
In accordance with a sixth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the first aspect, the second aspect or the third aspect, wherein when the output voltage of the power generator is controlled to be returned from the voltage lower than the rated voltage to the rated voltage, it is possible to control to the output voltage lower than the rated voltage after the continuing time is over the predetermined second threshold.
In accordance with the sixth aspect, after returning the output voltage of the power generator to the rated voltage, the output voltage is kept to be set to the rated voltage value until the predetermined time has passed, and it is possible to control to the output voltage lower than the rated voltage after the predetermined time has passed. In general, a reduction of the engine rotational speed is generated when returning the output voltage to the rated voltage and there is a risk that the output voltage control is again performed, however, in accordance with the present invention, since the restoration of the engine rotational speed is performed with keeping the rated voltage at a time when the rotational speed is reduced immediately after being returned to the rated voltage, the output voltage is not frequently changed in accordance with the present control. Accordingly, it is possible to stabilize the output voltage of the power generator.
Further, in accordance with a seventh aspect, there is provided an engine generator having an engine, a power generator driven by the engine, and an automatic voltage adjuster which inputs an output voltage of the power generator and an adjustment voltage command value from an external portion so as to control the output voltage of the power generator in correspondence to the input adjustment voltage command signal, wherein the engine generator comprising an engine rotational speed detector which detects a rotational speed of the engine, an engine controller which outputs an adjustment voltage command value of the automatic voltage adjuster in correspondence to a deviation value between an actually measured value by the engine rotational speed detector and a predetermined target value, a predetermined number of resistances obtained by connecting a combined resistance formed by a predetermined parallel and series to an adjustment voltage connection in anyone of command input terminal of the automatic voltage adjuster, and switch means which can switch the predetermined connection of the resistances in correspondence to the adjustment voltage command value of the engine controller.
In accordance with the seventh aspect, since a degree of the load applied to the power generator is judged on the basis of the engine rotational speed and the output voltage of the power generator is controlled in correspondence to the deviation value between the predetermined target value of the rotational speed and the actually measured value, that is, the degree of the change of the rotational speed, it is possible to the reduce the output voltage in correspondence to the magnitude of the sudden load change so as to lighten the load. Accordingly, it is possible to restrict the change width and the change time of the output voltage, the frequency and the like of the power generator to a minimum limit at the sudden load transient time by utilizing the rotational speed detector without detecting the output current, the output power or the like in the power generator side which is performed in the prior art, whereby it is possible to move to the stable operation. Accordingly, it is possible to obtain the voltage control apparatus of the engine generator which can be manufactured to be compact in a simple structure and at a low cost.
Further, a plurality of resistances and a plurality of switch means are combined and input to the adjustment voltage input terminal of the automatic voltage adjuster. As mentioned above, the input circuit is a significantly simple structure, however, since the combined resistance comprising a plurality of resistances is switched by turning on or off a plurality of switch means, it is possible to input the adjustment voltage command having multiple stages to the automatic voltage adjuster. Accordingly, it is possible to accurately control the output voltage of the power generator by a simple structure in correspondence to the rotational speed of the engine and/or the deviation value of the fuel injection amount.
In accordance with an eighth aspect, there is provided an engine generator having an engine, a power generator driven by the engine, and an automatic voltage adjuster which inputs an output voltage of the power generator and an adjustment voltage command value from an external portion so as to control the output voltage of the power generator in correspondence to the input adjustment voltage command signal, wherein the engine generator comprising an engine rotational speed detector which detects a rotational speed of the engine, fuel injection amount detecting means which detects a fuel injection amount of the engine, an engine controller which outputs an adjustment voltage command value of the automatic voltage adjuster in correspondence to a deviation value between a target value of the fuel injection amount with respect to an actually measured value of the rotational speed by the engine rotational speed detector and an actually measured value of the fuel injection amount by the fuel injection amount detecting means, a predetermined number of resistances obtained by connecting a combined resistance formed by a predetermined parallel and series to an adjustment voltage connection in anyone of command input terminal of the automatic voltage adjuster, and switch means which can switch the predetermined connection of the resistances in correspondence to the adjustment voltage command value of the engine controller.
In accordance with the eighth aspect, since a degree of the load applied to the power generator is judged on the basis of the engine fuel injection amount and the output voltage of the power generator is controlled in correspondence to the deviation value between the target value of the fuel injection amount with respect to the actually measured value of the engine rotational speed and the actually measured value of the fuel injection amount, that is, the degree of the change of the fuel injection amount, it is possible to the reduce the output voltage in correspondence to the magnitude of the sudden load change so as to lighten the load. At this time, since it is possible to control the output voltage of the power generator even in the case that the actual rotational speed is over the target value of the rotational speed in the first aspect, that is, the control start engine rotational speed, it is possible to know the load increase of the power generator at an early time so as to lighten the load. Accordingly, it is possible to restrict the change width and the change time of the output voltage, the frequency and the like of the power generator to a minimum limit at the sudden load transient time by utilizing the rotational speed detector and the fuel injection amount detecting means without detecting the output current, the output power or the like in the power generator side which is performed in the prior art, whereby it is possible to move to the stable operation. Accordingly, it is possible to obtain the voltage control apparatus of the engine generator which can be manufactured to be compact in a simple structure and at a low cost.
Further, a plurality of resistances and a plurality of switch means are combined and input to the adjustment voltage input terminal of the automatic voltage adjuster. Accordingly, the input circuit is a significantly simple structure, however, it is possible to input the adjustment voltage command having multiple stages to the automatic voltage adjusted by turning on or off a plurality of switch means. Accordingly, it is possible to accurately control the output voltage of the power generator by a simple structure in correspondence to the rotational speed of the engine and/or the deviation value of the fuel injection amount.
In accordance with a ninth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator comprising the steps of:
detecting an actually measured value of an engine rotational speed at every predetermined time; and
controlling an output voltage of the power generator on the basis of a time change rate of the actually measured value.
In accordance with the ninth aspect, since a degree of the load is judged on the basis of the time change rate of the actually measured engine rotational speed and the output voltage of the power generator is controlled in accordance with a magnitude of the load, it is possible to improve a response in comparison with the output voltage control in accordance with the deviation value of the injection amount mentioned above. That is, since the control amount in accordance with the deviation value of the injection amount is calculated on the basis of the result of the reduction of the engine rotational speed, it is possible to know the change in time in the case of being controlled in accordance with the time change rate of the engine rotational speed in comparison with the case of being controlled in accordance with the deviation value of the injection amount. Accordingly, since the time control can be earlier started even at the sudden load time so as to improve the response of the control, in accordance with the time change rate of the engine rotational speed, the reduction rate of the output voltage of the power generator is not increased, and the engine rotational speed can be early restored. Further, since no injection amount detector is required and it is possible to use the engine rotational speed detector employed for controlling the engine rotational speed, it is possible to more easily construct the control apparatus.
In accordance with a tenth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the ninth aspect, wherein when the time change rate of the actually measured value of the engine rotational speed is reduced to a level equal to or less than a predetermined value, the output voltage control of the power generator is started.
In accordance with the tenth aspect, since it is judged that the load is increased when the time change rate of the actual engine rotational speed is reduced to a level equal to or less than a predetermined value NT1, it is possible to know the load change earlier than the case of being controlled in accordance with the deviation value of the injection amount and to start the output voltage control of the power generator earlier even at the sudden load time. Accordingly, since the response of the control is improved, it is possible to early restore the engine rotational speed.
In accordance with an eleventh aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the ninth aspect, wherein the control is performed by changing the output voltage value of the power generator in accordance with the time change rate of the actually measured value of the engine rotational speed.
In accordance with the eleventh aspect, since the output voltage control is performed by judging that the load is large so as to set the output voltage value of the power generator low when the time change rate of the actual engine rotational speed is large and judging that the load is small so as to set the output voltage value of the power generator high when it is inversely small, the output voltage value can be set optimum in accordance with the load. Accordingly, it is possible to stably restore the engine rotational speed for a short time in spite of the degree of the load.
In accordance with a twelfth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the ninth aspect, the tenth aspect or the eleventh aspect, wherein the output voltage is maintained until at least third threshold or more of the control time has passed after starting the output voltage control of the power generator.
In accordance with the twelfth aspect, since in the case that the load of the power generator is small, the output voltage is maintained until at least the third threshold T3 or more of the control time has passed even when the engine rotational speed is restored for a short time after starting the output voltage control of the power generator, it is possible to securely restore the output voltage without changing the output voltage at a degree equal to or more than necessity.
In accordance with a thirteenth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the ninth aspect, the tenth aspect or the eleventh aspect, wherein when first threshold or more of the control time has passed after starting the output voltage control of the power generator, the output voltage control is stopped and a control of returning to the rated output voltage is performed.
In accordance with the thirteenth aspect, since the voltage reduction in accordance with the output voltage control of the power generator continues only a time equal or less than the first threshold T1 of the control time, it is possible to confirm the output voltage with the standard of the power generator and to secure a stability of the voltage of the power generator.
In accordance with a fourteenth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the thirteenth aspect, wherein when the actually measured value of the engine rotational speed becomes equal to or more than a predetermined fourth target value during the output voltage control, the output voltage control is stopped and a control of returning to the rated output voltage is performed.
In accordance with the fourteenth aspect, since the output voltage is returned to the rated output voltage when the actually measured value Ne of the engine rotational speed becomes equal to or more than a predetermined fourth target value (NeRxe2x88x92N4) after starting the output voltage control of the power generator, it is possible to securely restore the output voltage without reducing the output voltage at a degree equal to or more than necessity.
In accordance with a fifteenth aspect of the present invention, there is provided a method of controlling a voltage of an engine generator as cited in the thirteenth aspect, wherein the output voltage control is continued when the actually measured value of the engine rotational speed becomes equal to or less than a predetermined first target value during the output voltage control, and the output voltage control is stopped and a control of returning to the rated output voltage is performed when a third threshold shorter than the first threshold of the control time has passed after starting the output voltage control and the actually measured value of the engine rotational speed becomes equal to or more than a predetermined fourth target value higher than the predetermined first target value.
In accordance with the fifteenth aspect, since the voltage control is maintained until the third threshold T3 of the control time has passed after starting the output voltage control of the power generator, the output voltage can be stabilized without changing the output voltage even when the load is reduced for a short time. Further, after the third threshold T3 has passed, since the output voltage control is stopped when the actually measured value of the engine rotational speed becomes equal to or more than the fourth threshold N4 higher than the first threshold of the engine rotational speed, the output voltage control can be stabilized in accordance with a hysteresis characteristic of the monitored engine rotational speed and the output voltage is returned to the rated output voltage after the rotational speed is securely restored to the original value. Accordingly, it is possible to securely stabilize the output voltage.